Chip package structure and method for forming chip package

ABSTRACT

The present disclosure relates to a chip package structure and a method for forming a chip package. A package unit is formed from the chip and an encapsulant surrounding the chip to have an increased area. A redistribution layer is formed on the package unit to draw out to and redistribute input/output terminals on a surface of the chip. The redistribution layer is then electrically coupled to a leadframe or a printed circuit board by external and electrical connectors. The method and the package structure are suitable for providing a chip package having input/output terminals with high density, reducing package cost, and improving package reliability.

CLAIM OF PRIORITY

This application claims priority to Chinese Application No.201510283826.8, filed on May 28, 2015, which is hereby incorporated byreference.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

The present disclosure generally relates to the field of a chip package,and more particularly, to a chip package structure and a method forforming a chip package.

Description of the Related Art

A conventional method for forming a chip package includes the steps ofsingulating chips by cutting a wafer, attaching each chip to aleadframe, electrically coupling input/output pads on the chip to theleadframe by metal wires, and encapsulating the chip to form a chippackage. Such method of forming the chip package by using bonding wiresis not suitable for forming a chip package having input/output (I/O)terminals with a high density, because pins are provided around the chipand pitches between adjacent ones of the pins should be no less than apredetermined value for an encapsulant. The number of pins surroundingthe chip can be increased by increasing an area of the chip, in a casethat a chip package needs more I/O terminals. Nevertheless, the methodwill increase manufacture cost of the chip.

To solve the problem, a chip-scale package (i.e. CSP package) and aflip-chip package are developed. However, each of solder balls orconductive bumps occupy an area (typically larger than pads) of asurface of a chip. In a case that I/O terminals on the surface of thechip increases, the pitches between adjacent ones of the pads of the I/Oterminals decrease to a value which is too small to form the solderballs or the conductive bumps on the pads for electrical connection.Thus, the CSP package and the flip-chip package still do not satisfy therequirement of the chip package with I/O terminals having ultra-highdensity.

BRIEF DESCRIPTION OF THE DISCLOSURE

In view of this, the present disclosure provides a new method forforming a chip package and a new chip package structure for meeting therequirement of the chip package with I/O terminals having ultra-highdensity.

A method for forming a chip package, comprises:

singulating a chip from a wafer and providing pads of input/outputterminals on an active surface of the chip;

adhering the chip to a planar pad with the active surface facing upward;

filling spaces between adjacent ones of the plurality of chips with anencapsulant by a molding process, so that each of the plurality of chipsand the encapsulant surrounding it form a package unit;

forming an insulating layer having openings on the package unit, whereineach of the openings at least exposes a portion of each of the pluralityof pads;

forming a redistribution layer on the insulating layer which contactsexposed portion of each of the plurality of pads to redistribute theinput/output terminals; and

electrically coupling the redistribution layer to a leadframe or aprinted circuit board by external and electrical connectors.

Preferably, before electrically coupling the redistribution layer to theleadframe or the printed circuit board by the external and electricalconnectors, the method further comprises forming the external andelectrical connectors on the redistribution layer, cutting theencapsulant between the adjacent ones of the plurality of chips, andseparating the package unit from the plate.

Preferably, the external and electrical connectors are solder balls, andthe redistribution layer of the package unit is electrically coupled tothe printed circuit board with the solder balls.

Preferably, before forming the solder balls, the method further COMPOSESforming a protection layer on the redistribution layer and which exposesportions of the redistribution layer for forming the solder balls.

Preferably, the electrical and electrical connectors are conductivebumps, and the redistribution layer of the package unit is electricallycoupled to the leadframe with the conductive bumps.

Preferably, the external and electrical connectors are metal wires forelectrically coupling the redistribution layer to the leadframe, andafter forming the redistribution layer and before electrically couplingthe redistribution layer to the leadframe by the metal wires, theencapsulant is cut between the adjacent ones of the plurality of chips,and the package unit is separated from the plate.

Preferably, the encapsulant covers the package unit and the leadframe inthe molding process.

Preferably, two adjacent ones of the input/output terminals have a pitchsmaller than 120 micrometers.

A package structure, comprises:

a plurality of chips having a plurality of pads of input/outputterminals on an active surface of each chip;

an encapsulant surrounding each of the plurality of chips;

an insulating layer at least partially covering the active surface andhaving openings with each opening at least exposing a portion of each ofthe plurality of pads; and

a redistribution layer on the insulating layer and contacting exposedportion of each of the plurality of pads to redistribute theinput/output terminals.

Preferably, the package structure further comprises external andelectrical connectors, each of which has one end being electricallycoupled to the redistribution layer and the other end being electricallycoupled to a leadframe and a printed circuit board.

Thus, in the chip package structure and the method for forming a chippackage according to the present disclosure, a package unit is formedfrom the chip and an encapsulant surrounding the chip to have anincreased area. A redistribution layer is formed on the package unit todraw out and redistribute input/output terminals on a surface of thechip. The redistribution layer is then electrically coupled to aleadframe or a printed circuit board by external and electricalconnectors. The method and the package structure are suitable forproviding a chip package having input/output terminals with highdensity, reducing package cost, and improving package reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages and features of the presentinvention will become more fully understood from the detaileddescription given hereinbelow in connection with the appended drawings,and wherein:

FIG. 1 is a schematic diagram showing an example structure of a waferstructure having chips formed therein;

FIG. 2 is a schematic diagram showing an example structure after thechips are attached to a plate;

FIG. 3 is a cross-sectional view showing an example structure afterencapsulating the chips which have been attached to the plate;

FIG. 4 is an enlarged view showing a package unit in the examplestructure as shown in FIG. 2;

FIG. 5 is a top view showing an example structure after I/O terminals onthe active surface of the chip are drawn out to and redistributed on asurface of the package unit; and

FIG. 6 is a cross-sectional view showing the example structure as shownin FIG. 5 after I/O terminals on the active surface of the chip aredrawn out to and redistributed on a surface of the package unit.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE

Exemplary embodiments of the present disclosure will be described inmore details below with reference to the accompanying drawings. In thedrawings, like reference numerals denote like members. The figures arenot drawn to scale, for the sake of clarity. Moreover, some well knownparts may not be shown. For simplicity, the package structure havingbeen subject to several relevant process steps may be shown in onefigure. Some particular details of the invention will be described, suchas an exemplary structure, material, dimension, process step andfabricating method of the device, for a better understanding of thepresent invention. However, it can be understood by one skilled personin the art that these details are not always essential for but can bevaried in a specific implementation of the disclosure.

According to an embodiment of the present disclosure, there is provideda method for forming a chip package, including the following steps.

In step 1, chips are singulated to be individual ones by cutting awafer.

FIG. 1 is a structural diagram showing an example wafer structure havingchips therein. The wafer 1 is typically a silicon wafer, with electronicdevices and circuits formed therein. Each silicon wafer includes aplurality of chips 2 with an active surface, the active surface isprovided with a pad (not shown in FIG. 1) of a plurality of input/outputterminals (I/O terminals). The I/O terminals may be arranged with highdensity. For example, two adjacent ones of the I/O terminals may have apitch smaller than 120 micrometers, or preferably 100 micrometers, orpreferably 80 micrometers, or preferably 50 micrometers, or the like.The I/O terminals are arranged in high density to increase integrationlevel of the chip.

In step 2, after cutting the wafer, the chips having been separated fromeach other are attached to a plate with active surfaces facing upward.

FIG. 2 is a schematic diagram showing an example structure after thechips are attached to the plate. The chips 2 are arranged on the plate3, with a pitch between two adjacent ones, for example, ¼˜¾ of a width(or a length) of the chip. Each of the chips 2 has an active surfacefacing upward and a back surface (non-active surface) attached to theplate 3 so THAT the chips 2 are secured on the plate with apredetermined pitch. The plate 3 may be a metal one which can be easilyseparated from an encapsulant, or a film (for example, a glue film)which is stretched on a hard ring.

In step 3, an encapsulant is filled into spaces between adjacent ones ofthe plurality of chips by a molding process, so that each of theplurality of chips 2 and the encapsulant surrounding it form a packageunit.

The package structure formed after the molding process is shown in FIG.2. The encapsulant 4 fills spaces between adjacent ones of the chips 2by the following steps. A molding module is placed on the chips 2 tocover the chips 2, with a bottom of the molding module contacting theactive surfaces of the chips 2. An encapsulant 4 is injected between themolding module and the plate so that the encapsulant 4 fills spacesbetween adjacent ones of the chips 2. That is, the encapsulant surroundsall of the chips 2. It should be noted that the after the moldingprocess, the encapsulant 4 solidifies and has an upper surface typicallynot higher than the active surfaces of the chips 2 and a lower surfaceattached to the plate. The chips 2 are embedded in the encapsulant 4.The encapsulant may be epoxy resin, or similar insulating materialswhich can be easily separated from the plate 3. The encapsulant 4surrounds each of the chips 2 after the molding process. Each packageunit 5 includes a single chip 2 and a portion of the encapsulant 4surrounding the chip 2. In each package unit 5, the encapsulant 4surrounds the chip 2 and contacts side wall of the chip 2, which is asurface perpendicular to the active surface. Preferably, FIG. 3 is across-sectional view showing a structure after the molding process,including the encapsulant 4 and the chip 2. As shown in FIG. 3, an uppersurface of the encapsulant 4 is coplanar with active surfaces of thechips 2.

FIG. 4 is an enlarged view showing the package unit 5 as shown in FIG.2. As shown in FIG. 4, in the package unit 5, the encapsulant 4surrounds the chips 2, and has an upper surface which is coplanar withactive surfaces of the chips. Thus, an area of the package unit is muchlarger than those of the chips 2. Input/output terminals of the chipsmay be redistributed on the surface of the whole package unit, and arethen electrically coupled to an external circuit. Thus, the chips 2 mayhave the input/output terminals with higher density. That is, a pitch oftwo adjacent ones of the input/output terminals, i.e. a distance Abetween centers of two adjacent pads 6 as shown in FIG. 4, may besmaller than 120 micrometer, or preferably 100 micrometers, orpreferably 80 micrometers, or preferably 50 micrometers, or the like.The I/O terminals are arranged in high density to increase integrationlevel of the chip.

In step 5, an insulating layer is formed on the package unit and hasopenings with each opening at least exposing a portion of each of theplurality of pads.

In step 6, a redistribution layer is formed on the insulating layerwhich contacts exposed portion of each of the plurality of pads toredistribute the input/output terminals.

In step 7, the redistribution layer is electrically coupled to aleadframe or a printed circuit board by external and electricalconnectors.

FIGS. 5 and 6 are a top view and a cross-sectional view respectively,which show an example structure after I/O terminals on the activesurface of the chip are drawn out to and redistributed on a surface ofthe package unit.

As shown in FIGS. 5 and 6, after the step 4, an insulating layer 7 isformed on surfaces of all of the package units. The insulating layer 7may be provided at a central portion of each package unit, or extend tothe encapsulant of each package unit. Moreover, the insulating layer hasopenings which expose at least a portion of each pad 6. That is, atleast a portion of each pad 6 is exposed. The insulating layer 7 may bea layer of silicon dioxide, or a stack of silicon dioxide and siliconnitride.

After forming the insulating layer, a redistribution layer is formed onthe insulating layer, which is a patterned conductive metal layer andshown as the redistribution layer 8 as shown in FIG. 5. Theredistribution layer 8 is patterned into a plurality of conductivetraces which are separated from each other. Each conductive tracecontacts respective one pad 6 to draw out the I/O terminals of the chip2 to the conductive traces. The conductive traces may extend to thesurface of the encapsulant 4, and draw out the I/O terminals to thesurface of the encapsulant 4, but not only is located on the chips 2.External and electrical connectors 9 are used for electrically couplingthe redistribution layer to a leadframe or a printed circuit board, andhave an increased area for arrangement on the package unit, includingboth an area of the chip and an area of the encapsulant. Thus, more I/Oterminals may be drawn out on the package unit. Accordingly, thepatterned redistribution layer contacts exposed portions of the pads,for redistributing locations of the input/output terminals, whicheffectively increases an arrangement area of the I/O terminals. Thepitches of the I/O terminals of the chips 2 can be greatly decreased.

In this embodiment, the external and electrical connectors may be solderballs. The method for forming the package structure according to anembodiment of the present disclosure, before step 7, further includesforming the external and electrical connectors 9 on the redistributionlayer, cutting the encapsulant 4 between adjacent ones of the chips 2,and separating each package unit 5 from the plate 3, to form packageunits which are separated from each other. Then, in step 7, the externaland electrical connectors of each package unit are electrically coupledto a leadframe or a printed circuit board to provide electricalconnections between the I/O terminals on the chip of the package unitand the external circuit.

Specifically, the external and electrical connectors are solder balls,such as tin solder balls, and the redistribution layer of the packageunit is electrically coupled to the printed circuit board with thesolder balls after the package unit is separated from the plate. In apreferable embodiment, before forming the solder balls, the methodfurther includes forming a protection layer (not shown in the figure) onthe redistribution layer which exposes portions of the redistributionlayer for forming the solder balls. Thus, the solder balls are separatedfrom each other with a distance and a short circuit may be avoided.

Moreover, the electrical and electrical connectors may also beconductive bumps, such as Cu bumps, and the redistribution layer of thepackage unit is electrically coupled to the leadframe with theconductive bumps. After the package unit is electrically coupled to theleadframe, the encapsulant covers the package unit and the leadframe inthe molding process. The term “cover” here means incompleteencapsulation, with leads of the leadframe being exposed outside theencapsulant for being electrically coupled to the external circuit.

In other embodiments, the external and electrical connectors may bemetal wires, and the redistribution layer is electrically coupled to theleadframe by the metal wires. Thus, the method for forming a packagestructure according to an embodiment of the present disclosure furtherincludes cutting the encapsulant between the adjacent ones of theplurality of chips, and separating the package unit from the plate,after forming the redistribution layer and before electrically couplingthe redistribution layer to the leadframe by the metal wires. Afterseparating the package unit, one end of the metal wire is electricallycoupled to the redistribution layer of the package unit, and the otherend of the metal wire is electrically coupled to the leadframe, and moreparticularly to the leads of the leadframe. After the package unit iselectrically coupled to the leadframe by the metal wires, theencapsulant covers the package unit and the leadframe in the moldingprocess. The term “cover” here means incomplete encapsulation, withleads of the leadframe being exposed outside the encapsulant for beingelectrically coupled to the external circuit.

Moreover, according to an embodiment of the present disclosure, there isprovided a package structure as shown in FIG. 6. The chip packagestructure mainly includes a chip 2, an encapsulant 4, an insulatinglayer 7, a redistribution layer 8, and external and electricalconnectors 9, each of which has one end being electrically coupled tothe redistribution layer and the other end being electrically coupled toa leadframe and a printed circuit board.

The chip 2 has an active surface provided with pads 6 of input/outputterminals. Two adjacent ones of the input/output terminals may have apitch smaller than 120 micrometers, or preferably 100 micrometers, orpreferably 80 micrometers, or preferably 50 micrometers, or the like.The two adjacent ones of the I/O terminals have a pitch which is toosmall to arrange external and electrical connectors 9 directly on thepads 6.

The encapsulant 4 surrounds the chip 2 and contacts a side wall (i.e. asurface perpendicular to the active surface) of the chip 2, and has asurface which is coplanar with the active surface of the chip, oralternatively, lower than the active surface. Thus, an area of thepackage unit including the chip 2 and the encapsulant surrounding it ismuch larger than that of the chip 2. Input/output terminals of the chipsmay be redistributed on the surface of the whole package unit, and thenbe electrically coupled to an external circuit. Thus, the chips 2 mayhave the input/output terminals with higher density.

The insulating layer 7 at least partially covers the active surface andhas openings with each opening at least exposing a portion of each ofthe plurality of pads. In an embodiment, the insulating layer may extendto the encapsulant 4. The insulating layer may be made of silicondioxide, or the like.

The redistribution layer 8 is arranged on the insulating layer andcontacts exposed portion of each of the plurality of pads 6 toredistribute the input/output terminals. The redistribution layer 8extends to a surface of the encapsulant 4, which increases an area ofthe external and electrical connectors 9 for arrangement, and an area ofthe I/O terminals. The chip 2 will be allowed to have I/O terminals withhigh density. The external and electrical connectors may be on selectedform the group consisting of solder balls, conductive bumps, and metalwires.

Thus, in the chip package structure and the method for forming a chippackage according to the present disclosure, a package unit is formedfrom the chip and an encapsulant surrounding the chip to have anincreased area. A redistribution layer is formed on the package unit todraw out and redistribute input/output terminals on a surface of thechip. The redistribution layer is then electrically coupled to aleadframe or a printed circuit board by external and electricalconnectors. The method and the package structure are suitable forproviding a chip package having input/output terminals with highdensity, reducing package cost, and improving package reliability.

Although various embodiments of the present invention are describedabove, these embodiments neither present all details, nor imply that thepresent invention is limited to these embodiments. Obviously, manymodifications and changes may be made in light of the teaching of theabove embodiments. These embodiments are presented and some details aredescribed herein only for explaining the principle of the invention andits actual use, so that one skilled person can practice the presentinvention and introduce some modifications in light of the invention.The invention is intended to cover alternatives, modifications andequivalents that may be included within the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. A method for forming a chip package, comprising:singulating a plurality of chips from a wafer, wherein each of saidplurality of chips is provided with a plurality of pads of input/outputterminals on an active surface; attaching said plurality of chips to aplate with active surfaces facing upward; filling spaces betweenadjacent ones of said plurality of chips with an encapsulant by amolding process to provide a plurality of package units, wherein saidactive surfaces are exposed from said encapsulant and each of saidplurality of package units comprises one of said plurality of chips anda portion of said encapsulant surrounding said one of said plurality ofchips; forming an insulating layer on said active surfaces and saidencapsulant, wherein said insulating layer has openings extendingthrough said insulating layer to expose said plurality of pads; forminga redistribution layer which covers said insulating layer and contactingsaid plurality of pads through said openings to redistribute saidinput/output terminals; cutting said encapsulant between two adjacentchips, separating said plurality of package units from said plate aftercutting said encapsulant; and electrically coupling said redistributionlayer in each of said plurality of package units to a leadframe or aprinted circuit board by external and electrical connectors, whereinsaid encapsulant contacts a side wall of said chip, and has a surfacewhich is coplanar with said active surface, or lower than said activesurface, said active surface is configured as upper surface of saidplurality of chips in contact with said plurality of pads.
 2. The methodaccording to claim 1, before cutting said encapsulant between saidadjacent ones of said plurality of chips, further comprising formingsaid external and electrical connectors on said redistribution layer. 3.The method according to claim 2, wherein said external and electricalconnectors are solder balls, and said portion of redistribution layer iselectrically coupled to said printed circuit board with said solderballs.
 4. The method according to claim 3, before forming said solderballs, further comprising forming a protection layer on saidredistribution layer and which exposes portions of said redistributionlayer for forming said solder balls.
 5. The method according to claim 2,wherein said electrical and electrical connectors are conductive bumps,and said portion of redistribution layer is electrically coupled to saidleadframe with said conductive bumps.
 6. The method according to claim1, wherein said external and electrical connectors are metal wires forelectrically coupling said portion of redistribution layer to saidleadframe.
 7. The method according to claim 6, after separating saidplurality of package units, further comprising encapsulating one of saidplurality of package units and said leadframe by a second moldingprocess.
 8. The method according to claim 1, wherein two adjacent onesof said input/output terminals have a pitch smaller than 120micrometers.